Motorola Droid Turbo Android 5.1 Lollipop update is now available after months of waiting. In May 2015 the device was reported to get the firmware as the soak test but it was eventually got delayed. Finally it's now available for download via Over the Air[OTA].
You should probably have received the update notification on your device. If you have then just follow the on-screen instructions to download the update. If there isn't anything, then you can force check for the update manually.
To download the Settings, you should head to Settings > About Phone > System Update and then finally hit tap on Check for Update option.